An application of petri nets in structured analysis

Data flow diagrams (DFD), which originated from the popular Structured Analysis methodology [4, 5, 11] can be used to model a system in the form of a network of components and interfaces among them. When a system is too complex to be shown in a single diagram, it can be partitioned into subsystems, which can be further partitioned until each component can be described in a simple diagram made of primitive processes. Each of these successive partitions is documented in a separate DFD, so that we have a hierarchical structure. In order to ensure consistency, all data flows into/out of a child diagram must be represented on the parent diagram by the same data flows into/out of the corresponding bubble. We are also free to refine data flows into more detail on the child diagrams, so that we have a parallel decomposition of both data and processes. A labeling convention for bubbles and diagrams has been included to facilitate traceability between different levels of abstraction. Furthermore, these labels can be used for tracing the correspondence between the requirements specification and the final design.